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Medication · Knee Pain

Anti-inflammatories and Knee Pain

Anti-inflammatories are the most used — and most misused — medication for knee pain. Used well, they relieve. Used long-term and without judgement, they cause harm. This is the clear guide.

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COX-1/COX-2Enzymes that NSAIDs block
≤ 7–14 daysIdeal duration in acute pain
Topical first lineRecommended in knee osteoarthritis
Do not regenerateThey relieve symptoms, they do not halt osteoarthritis
What they are

What is an Anti-inflammatory (NSAID)?

NSAID stands for non-steroidal anti-inflammatory drug. This group of medicines — ibuprofen, naproxen, diclofenac, etoricoxib, among others — blocks the cyclo-oxygenase (COX-1 and COX-2) enzymes, reducing the production of prostaglandins. Prostaglandins are the chemical messengers that cause pain, inflammation, heat and swelling.

By reducing them, the NSAID relieves pain and inflammation at the same time. This is what sets them apart from a "pure" analgesic such as paracetamol, which relieves pain but has a minimal anti-inflammatory effect.

It is important not to confuse three different things that people call "anti-inflammatory":

NSAIDs treat the symptom — pain and inflammation. They do not correct the cause of knee pain, nor do they regenerate cartilage. They are a tool, not the solution.

NSAID vs. Corticosteroid vs. Paracetamol

NSAID (non-steroidal)

Ibuprofen, naproxen, diclofenac, etoricoxib. Relieves pain and inflammation. Gastrointestinal, renal and cardiovascular risks.

Corticosteroid (steroid)

E.g. prednisolone or a corticosteroid injection. A potent anti-inflammatory, but with a different profile of effects — occasional, monitored use.

Paracetamol

Analgesic and antipyretic. Almost no anti-inflammatory effect, but much safer. A good baseline and complement.

What they do for the knee

Why They Are Worth Taking — In the Right Situations

Pain is not just a nuisance: it hurts, it makes you limp, it robs you of sleep, and it prevents physiotherapy and exercise. Controlling pain and inflammation at the right times allows you to recover movement — which is, in fact, the real treatment.

In knee osteoarthritis (gonarthrosis)

  • Osteoarthritis has a genuine inflammatory component (synovitis) — it is not only "wear and tear". NSAIDs act on that inflammation.
  • International recommendations (OARSI, ACR, NICE) place the topical NSAID gel as first line in knee osteoarthritis: effective and with far less risk than the tablet.
  • The oral NSAID is indicated for flare-ups, in short courses, and not as a permanent daily tablet.
  • By lowering the pain, they allow you to do physiotherapy, strengthening and weight loss — which are what really change the course of the disease.

In acute knee pain (acute gonalgia)

  • In a sprain, tendinitis, osteoarthritis flare-up, bursitis or after trauma, a short course of NSAID reduces pain and swelling and speeds the return to function.
  • They are combined with relative rest, ice, elevation and a gradual return to movement.
  • Practical rule: the lowest effective dose, for the shortest possible time — usually a few days to two weeks.
  • If severe acute pain does not improve within a few days, or the knee locks/swells markedly, the answer is to look at the cause — not to increase the anti-inflammatory.
The difference between them

Not All Anti-inflammatories Are the Same

They all relieve pain, but they differ in duration of action, potency and — above all — risk profile. The right choice depends on you: age, stomach, kidneys, heart and other medicines. This table is a guide, not a prescription.

DrugHow it is usedProfileCardiovascular risk
Ibuprofen Short-acting, 2–3× a day. Flexible, good for short courses and occasional pain. Moderate potency. The most widely used over the counter. Moderate
Naproxen Long-acting, 1–2× a day. Useful when more sustained relief is needed. Good potency. The most favourable cardiovascular profile of the group. Lower
Diclofenac / Aceclofenac Potent, very effective for pain. Also available as a topical gel. Strong relief, but among those that most burden the heart when taken orally. Higher
Coxibs — Etoricoxib / Celecoxib (COX-2) 1× a day (etoricoxib). Selective — designed to spare the stomach. Fewer gastric ulcers and bleeds. The choice when there is digestive risk. Monitor (heart/BP)
Acemetacin (Rantudil®) An indometacin derivative, potent. Prolonged release, 1–2× a day. Very effective in osteoarthritis and inflammatory pain. Demanding on the stomach; may cause headaches and dizziness. Moderate
Nimesulide Short courses, at most ~15 days. Effective, but requires caution with the liver. Moderate
Topical NSAID (gel) Applied over the knee, 3–4× a day. Diclofenac or ibuprofen gel. First line in knee osteoarthritis. Minimal systemic absorption. Very low
Paracetamol (not an NSAID) Up to 3 g/day with guidance. A safe analgesic baseline. No relevant anti-inflammatory effect, but very well tolerated. Very low
Golden rule: never combine two oral anti-inflammatories at the same time (e.g. ibuprofen + diclofenac, or NSAID + aspirin) — the relief does not increase, but the risks multiply. The topical gel can generally be combined safely with paracetamol.

What about coxibs (COX-2 inhibitors)?

Coxibs — celecoxib and etoricoxib (rofecoxib/Vioxx was withdrawn from the market) — block mainly COX-2, the enzyme linked to inflammation, sparing COX-1, which protects the stomach.

The result: they relieve osteoarthritis pain as well as the classic NSAIDs, but with considerably fewer gastric ulcers and digestive bleeds. They are therefore the preferred choice for those with gastric risk (advanced age, previous ulcer).

The catch is the heart: they retain fluid, raise blood pressure and increase cardiovascular risk. They are avoided in heart disease, heart failure or previous stroke. And, unlike aspirin, they do not protect the heart or thin the blood.

What about Rantudil® (acemetacin)?

Rantudil® is the brand name for acemetacin, an anti-inflammatory derived from indometacin — one of the most potent in the group.

It is effective in osteoarthritis and more intense inflammatory pain, often as a single daily prolonged-release dose. It is not a first-line NSAID for mild pain — it is reserved for when more potency is needed.

In return, it inherits the effects of indometacin: it is demanding on the stomach and may cause headaches, dizziness or drowsiness. It retains all the gastrointestinal, renal and cardiovascular precautions of the other NSAIDs.

The dangers

Where Anti-inflammatories Cause Harm

NSAIDs are not "just a tablet for the pain". Prolonged use, at high doses or in the wrong people, causes serious complications — some of them silent until they become severe.

Stomach and intestine

Gastritis, ulcer and digestive bleeding. Greater risk in the elderly, with a previous ulcer or when taking corticosteroids, anticoagulants or certain antidepressants. Warning signs: black stools, severe stomach pain, vomiting blood.

Kidneys

They reduce blood flow to the kidney. Dangerous in kidney disease, dehydration and advanced age. The combination of NSAID + diuretic + blood-pressure medicine (ACE inhibitor/ARB) can precipitate acute kidney injury.

Heart and circulation

They increase the risk of heart attack, stroke and heart failure, especially diclofenac and the coxibs. To be avoided in those with known heart disease. Naproxen carries the lowest risk.

Blood pressure

They raise blood pressure and reduce the effectiveness of antihypertensive medicines. Anyone with hypertension should use them with care and monitor their blood pressure.

Interactions

Dangerous with anticoagulants/warfarin (bleeding), lithium and methotrexate (they raise the levels). Always tell your doctor about everything you take.

Liver, allergy and pregnancy

Nimesulide requires caution regarding the liver. They may trigger attacks in sensitive asthmatics. Avoid in pregnancy, especially in the 3rd trimester.

⚠ Stop and seek medical help if you develop: black or bloody stools · severe stomach pain · reduced urine output, swelling of the legs · shortness of breath or palpitations · an allergic skin reaction. These signs may indicate a serious complication of anti-inflammatories.
Practical advice

How to Take Anti-inflammatories Safely

If they are genuinely needed, these simple rules greatly reduce the risk without losing effectiveness.

1

Lowest dose, shortest time

The lowest effective dose and for the shortest possible time. In acute pain, think in terms of days to two weeks — not months.

2

Always with food

Taking them with meals or after eating protects the stomach. Never on a prolonged empty stomach.

3

Start with the gel and paracetamol

In knee osteoarthritis, the NSAID gel and paracetamol resolve many cases at a fraction of the risk of the tablet.

4

Protect the stomach if you are at risk

If you are over 65, have a previous ulcer or take other risk medicines, your doctor may add a gastric protector (PPI).

5

Never two NSAIDs together

One at a time. Do not add ibuprofen + diclofenac, nor NSAID + aspirin, without medical advice.

6

Pause on sick days

If you have vomiting, diarrhoea or fever with dehydration, temporarily stop the NSAID (and diuretics/blood-pressure medicines) and rehydrate — it protects the kidneys.

7

Always tell your doctor

Kidney disease, heart disease, hypertension, ulcer, anticoagulants or pregnancy completely change the choice of drug.

8

If you always need it, reassess

Depending on the anti-inflammatory every day is a sign that the cause needs to be examined and treated — not masked.

Sport after a knee replacement? Yes. A knee replacement is not the end of an active life — on the contrary, the goal of surgery is to restore pain-free mobility. Most patients return to low- and medium-impact activities: walking, swimming, water aerobics, cycling, golf, hiking, doubles tennis and recreational skiing. It is only advisable to avoid high-intensity repetitive impact (long-distance running, jumping and contact sports), which accelerates implant wear.

Related: Knee osteoarthritis · Knee injections · Knee pain — where to start

Frequently Asked Questions

Questions about Anti-inflammatories for the Knee

Not as a prolonged habit. Daily, continuous use of oral anti-inflammatories greatly increases gastrointestinal, renal and cardiovascular risk. In chronic osteoarthritis pain, prefer the topical gel and paracetamol as a baseline, and reserve the tablet for flare-ups, in short courses. If you feel you need it every day, it is a sign that the cause should be assessed.
Ibuprofen is short-acting and flexible for occasional pain. Naproxen lasts longer (1–2 doses a day) and has the best cardiovascular profile — good when more sustained relief is needed. Diclofenac is very potent, but among those that most burden the heart when taken orally, so it is avoided in heart disease. The right choice depends on your stomach, kidneys, heart and other medication.
It only relieves the symptoms — pain and inflammation. No anti-inflammatory regenerates cartilage or halts the progression of osteoarthritis. What really changes the course is weight loss, muscle strengthening and adapted activity. The NSAID is useful precisely because it lets you do that with less pain.
It works — and for knee osteoarthritis international recommendations place it as first line. The gel reaches the superficial joint of the knee with good effectiveness and minimal systemic absorption, which means far less gastrointestinal, renal and cardiovascular risk than the tablet. For many people it is the most sensible option to start with.
Two oral anti-inflammatories at the same time — never: they do not relieve more and they multiply the risks. Paracetamol, however, can generally be combined safely with an NSAID, because it acts differently. A common and safe strategy is paracetamol as a baseline and the NSAID (preferably as a gel) at times of greater pain.
With great care and ideally only under medical guidance. NSAIDs raise blood pressure, reduce the effectiveness of antihypertensive medicines, burden the kidneys and increase cardiovascular risk. In these cases the topical gel and paracetamol are preferred, and prolonged oral use is avoided. Always tell your doctor about all your conditions and medicines.
Coxibs (celecoxib, etoricoxib) are anti-inflammatories that block mainly COX-2, the inflammation enzyme, sparing COX-1, which protects the stomach lining. They therefore cause fewer ulcers and digestive bleeds than the classic NSAIDs, making them the preferred choice for those with gastric risk. But they are not safer for the heart: they retain fluid, raise blood pressure and increase cardiovascular risk, so they are avoided in heart disease. Unlike aspirin, they do not protect the heart.
Rantudil® is acemetacin, an anti-inflammatory derived from indometacin and one of the most potent. It is used in osteoarthritis and more intense inflammatory pain, often as a single daily prolonged-release dose. It is not the first choice for mild pain: it is reserved for when more potency is needed. As it inherits the effects of indometacin, it is demanding on the stomach and may cause headaches or dizziness, keeping the same gastrointestinal, renal and cardiovascular precautions as the other NSAIDs.
In acute pain, the rule is the lowest effective dose for the shortest possible time — usually a few days up to about two weeks. If after a few days the severe pain does not improve, or the knee swells markedly or locks, the next step is to assess the cause, not to prolong or increase the anti-inflammatory.
The cost depends on the treatment pathway. SIGIC (Portuguese NHS): with a surgery voucher, the procedure is fully covered — no cost to the patient. Health insurance / subsystems: contracted surgery, according to your plan. Private: a personalised quote — as a guide, from €3,000 for arthroscopy (meniscus, ligaments or cartilage, including anterior cruciate ligament reconstruction) and from €8,000 for knee replacement. Final prices depend on the clinical case, hospital and implants. For an exact quote, book an appointment or see prices & quotes.
NC

Dr. Nuno Camelo Barbosa

Orthopaedic Surgeon · Knee Subspecialist
Hospital Lusíadas Porto · Hospital Misericórdia Vila do Conde · Paços de Ferreira

Do you rely on anti-inflammatories for your knee?

This page is general information and does not replace a consultation. Needing them frequently is a sign that the cause of the pain should be assessed — to treat the problem, not merely mask the symptom.

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Dr. Nuno Camelo Barbosa
Dr. Nuno Camelo Barbosa
Orthopaedic surgeon · Knee surgery subspecialty
Peer reviewer (AJSM · KSSTA · OJSM · JEO)
Last medically reviewed: 24 July 2026
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